1. Field of the Invention
The present invention relates generally to a radiation therapy devices and a method of radiation therapy, and more particularly, to radiation therapy devices and radiation therapy methods that use predictive organ dynamics data.
2. Discussion of Related Art
Conventional radiation therapy typically involves directing a radiation beam at a tumor in a patient to deliver a predetermined dose of therapeutic radiation to the tumor according to an established treatment plan. This is typically accomplished using a radiation therapy device such as the device described in U.S. Pat. No. 5,668,847 issued Sep. 16, 1997 to Hernandez, the contents of which are incorporated herein for all purposes.
The radiotherapy treatment of tumors involves three-dimensional treatment volumes which typically include segments of normal, healthy tissue and organs. Healthy tissue and organs are often in the treatment path of the radiation beam. This complicates treatment, because the healthy tissue and organs must be taken into account when delivering a dose of radiation to the tumor. While there is a need to minimize damage to healthy tissue and organs, there is an equally important need to ensure that the tumor receives an adequately high dose of radiation. Thus, the goal of radiation is to administer a treatment that has a high probability of tumor control while providing an acceptably low probability of complications in normal tissue.
With new image guided and adaptive radiotherapy techniques, a wealth of information about the patient geometry is obtained, and it is desirable to use this information to tailor the treatment for complication-free tumor control at every step in the treatment. This is difficult because the three-dimensional treatment volumes for the tumor typically also include normal organs. Thus healthy tissue and organs must be taken into account when delivering a dose of radiation to the tumor, and each type of tissue has a different type of response to varying degrees of radiation. While there is a need to minimize damage to healthy tissue and organs, there is an equally important need to choose a prescription in which the tumor receives an adequately high dose of radiation. Cure rates for many tumors are a sensitive function of the dose they receive, just as complication rates in normal organs are a function of the dose that they receive. Therefore, it is useful to have as much information as possible to understand how a certain type of tumor and certain normal structures have responded to radiation in other patients. It would be essential to monitor these quantities both during treatment during the follow up process.
Another factor that adds complexity to the planning process is the fact that many organs change size, shape and position from day to day. This also affects the prescription because margins must be added to these structures to account for the likely extent of the changes. A better understanding of the likely effect of these factors could result in a more accurate plan and higher probability of complication free tumor control.
FIG. 1 schematically shows a radiation therapy machine 10 that includes a gantry 12 which can be swiveled around a horizontal axis of rotation 14 in the course of a therapeutic treatment. A treatment head 16 is fastened to a projection of the gantry 12. A linear accelerator (not shown) is located inside gantry 12 to generate the high energy radiation required for the therapy. The axis of the radiation bundle emitted from the linear accelerator and the gantry 12 is designated by beam path 18. Electron, photon or any other detectable radiation can be used for the therapy.
During a course of treatment, the radiation beam is trained on treatment zone 20 of an object 22, for example, a patient who is to be treated and whose tumor lies at the isocenter of the gantry rotation. Several beam shaping devices are used to shape radiation beams directed toward the treatment zone 20. For example, a multileaf photon collimator and a multileaf electron collimator can be arranged to shape the radiation beams. Each of these collimators may be separately controlled and positioned to shape beams directed at treatment zone 20.
Accordingly, it is an object of the present invention to tally informative statistics on the amount of dose required to treat specific types of tumors, and on the tolerance levels of specific normal tissues.
It is another object of the present invention to compile changes in the size and shape for each type of tissue and tumor and use the compiled changes with informative statistics to predict how organs will respond throughout the course of therapy.